R35GM126929 ORIGINAL PROJECT SUMMARY/ABSTRACT Tissue repair is essential to multicellular organisms that occasionally encounter a hostile environment. The ability to rapidly repair and restore function to barrier tissues is critical to organismal survival and is highly conserved. My laboratory pioneered the use of Drosophila larvae to study postembryonic epidermal wound healing. Over the past eleven years (9 of them funded by R01GM083031; Genetic control of postembryonic wound healing in Drosophila) we have investigated the signaling mechanisms that initiate wound closure, that recruit inflammatory macrophage-like cells to the wound, that actually orchestrate wound-induced cell migration, and that mediate the curious phenomenon of wound-induced epidermal cell-cell fusion. This NIGMS R35 MIRA application is intended to provide more stable and flexible funding to my laboratory as it continues to pursue important cellular and mechanistic questions regarding organismal tissue repair responses. Our long- term goal is to identify the full suite of genes that initiate each important wound response (migration, cell shape change, dedifferentiation, fusion, inflammation) and understand how these genes function and work together to orchestrate a successful wound repair program. Our work over the next five years will focus on three essential questions that emerge naturally from our ongoing studies: 1. How does epigenetic reprogramming and a coordinated transcriptional response in wound edge cells help facilitate closure? This question emerges from our observation that some epigenetic regulators are cleared from wound edge cells and others, along with certain transcription factors, are directly required for wound closure. A major effort will be devoted to understanding the transcriptional and epigenetic changes that are necessary for healing at the wound edge. 2. We have now set up a viable platform for identifying and studying the function of genes that are necessary for the curious phenomenon of wound-induced cell-cell fusion. This effort is likely to lead to major novel insights into how the understudied process of epithelial cell-cell fusion is controlled and orchestrated. 3. How do blood cells adhere to and spread at a wound to serve their function of clearing cellular debris? We have now identified at least one signaling pathway (Vascular Endothelial Growth Factor [VEGF] signaling) that is required for blood cell spreading at wound sites. This suggests that attachment and spreading are genetically separable events and we have developed a strategy for both identifying more players in this process and studying the function of known players that act downstream of VEGF in this context. My lab's substantial history of creative high-impact publications on diverse aspects of tissue repair suggests strongly that we will continue in this vein, especially if our ongoing grant-writing burden is reduced. Our system complements others in the field and the likelihood of continued novel basic insight into how organisms cope with tissue damage at the cellular and molecular/genetic levels is high.